The world’s simplest climate model. It is not really modelling climate, just plugging in the absorptivity of the sun’s energy coming to earth and the emissivity of the longwave radiation leaving the earth. It does calculate the temperature of the earth as a function of the day of year. It assumes that the earth is isothermal and does not have any thermal mass.
In the line count I exclude the definition of constants. For the sake of readability I have gone two over the number of lines.
And if you don’t like the temperature it is a simple matter to adjust the sun’s output, or the emissivity or absorptivity of the earth! 
No need to move!
Another interesting experiment is to equate the emissivity and absorptivity and then adjust them.
With the temperature calculation inside a 4th root the temperature stays fairly stable. (1.7% variation in temperature for a 6.8% variation in heat flux over the course of a year)
#= Calculate the temperature of the earth using the simplest model=#
using Unitful, Plots
p_sun = 386e24u"W" # power output of the sun
radius_a = 6378u"km" # semi-major axis of the earth
radius_b = 6357u"km" # semi-minor axis of the earth
orbit_a = 149.6e6u"km" # distance from the sun to earth
orbit_e = 0.017 # eccentricity of r = a(1-e^2)/(1+ecos(θ)) & time ≈ 365.25 * θ / 360 where θ is in degrees
a = 0.75 # absorptivity of the sun's radiation
e = 0.6 # emmissivity of the earth (very dependent on cloud cover)
σ = 5.6703e-8u"W*m^-2*K^-4" # Stefan-Boltzman constant
temp_sky = 3u"K" # sky temperature
# constants defined above and not included in the code
t = (0:0.25:365.25)u"d" # day of year
θ = 2*π/365.25u"d" .* t # approximate angle around the sun
r = orbit_a * (1-orbit_e^2) ./ (1 .+ orbit_e .* cos.(θ)) # distance from sun to earth
area_projected = π * radius_a * radius_b # area of earth facing the sun
ec = sqrt(1-radius_b^2/radius_a^2) # eccentricity of earth
area_surface = 2*π*radius_a^2*(1 + radius_b^2/(ec*radius_b^2)*atanh(ec)) # surface area of the earth
q_in = p_sun * a * area_projected ./ (4 * π .* r.^2) # total heat impacting the earth
temp_earth = (q_in ./ (e*σ*area_surface) .+ temp_sky^4).^0.25 # temperature of the earth
plot(t*u"d^-1", temp_earth*u"K^-1" .- 273.15, label = false, title = "Temperature of Earth", xlabel = "Day", ylabel = "Temperature [C]")
